That is the time to give to allow the temp in your vessel equilibrate from adding the hot decoction portion into your mash tun.

Anyone that does some scheduling decoction on a fairly regular basis help with a question. I tried a decoction and my schedule indicated 1.6 gals as the volume. So for a thick decoction I did 1.5 gal of somewhat drained grains and then added enough liquid from the mash tun to make the grains "slump". When I finished boiling this volume and add it into the mash tun once again the temp was off by about 14 degrees below the target temp. This has happened twice!! All the other schedule steps the temps are almost perfect. What am i doing wrong??

I'm trying to setup a decoction, but I'm having a hard time figuring out the fields. On the surface, they seem pretty straight-forward, but after plugging in some numbers and experimentally changing them, I think there is a lot more to it than what I see. Here are some problems I'm having, hoping someone can explain what I'm missing.

1) The Decoction Vessel is presumably the kettle that some of the grist will be transferred to for the boil; and then later be transferred from, when adding it back to the original mash tun vessel. But if you create a Rest step in the schedule right after the Decoction step, it's Final Temperature will be as if the entire mash is in the Decoction Vessel kettle. If I change the Decoction Vessel to my normal cooler mash tun, the rest of the schedule looks good, but that doesn't seem like what I'm supposed to do in BTP. Does the schedule assume the Decoction vessel is the mash tun for the rest of the schedule?

2) Isn't Boil Duration the amount of time that you want to boil the decoction? If so, then why does changing it auto-adjust the Decoction Volume number? Changing Boil Output does the same thing. I am guessing that this is because BTP is smartly calculating boil-off reductions based on both the length and the vigorousness of the boil, so that the remaining amount at the end of the boil will raise the mash tun temperature to the target. Is that correct, or is something else going on?

Docbee, when I try it, I'll let you know if I end up 14 degress low, too.

Bump -- I want to revisit this unresolved problem, because I'm trying to setup another decoction recipe, and my #1 above is still bugging me. Is it a bug that the vessel becomes the decoction kettle instead of my cooler mash tun for the rest of the mash? Or am I setting up the decoction step incorrectly? Thanks.

Yes, it is a very good article, and attaching the example file was genius! But I read it and loaded your example file before I re-posted my questions. Your sample file has the same problem as mine. Your Mashtun and Decoction Pot vessels' "Heat Transfer Coefficients" aren't as far apart as mine are, though, so you can't as easily see the effect of having the wrong vessel being used in the calculations for the next rest. Here is an example to illustrate what I'm talking about:

Take the recipe that is attached to the wiki article, and open the schedule. The "1st Decoction" step is going to raise the mash tun to 145 degrees, right? After 15 minutes, note that the "Main Mash 1st Sac Rest" final temperature has dropped to 141.8 degrees. Question: Did BTP calculate that 3.2 degree drop using the "Heat Transfer Coefficient" of the Mashtun or the Decoction Pot? Since that rest is happening in the Mashtun (the Decoction Pot is now empty, after all!), it should have been the Mashtun's "Heat Transfer Coefficient", right? But it wasn't. Here's the proof: Go to the Equipment list and edit your Decoction Pot's "Heat Transfer Coefficient" by arbitrarily setting it to 5.0. Then return to the schedule and notice that that final temp of the "Main Mash 1st Sac Rest" has changed to 138.7 degrees. Why should changing the Decoction Pot's value affect the temperature drop of a rest in the Mashtun vessel? On the other hand, if you then edit the Mashtun's "Heat Transfer Coefficient" to, say, 10.0, the "Main Mash 1st Sac Rest" final temp remains unchanged at 138.7, proving the Mashtun's heat value has no bearing on the rest's temperature drop.

I hope I have finally explained this clearly enough that Jeff and crew can understand what I mean, and either tell me where my assumptions are wrong, or say that it is a bug that can be addressed.

Brant wrote:Take the recipe that is attached to the wiki article, and open the schedule. The "1st Decoction" step is going to raise the mash tun to 145 degrees, right? After 15 minutes, note that the "Main Mash 1st Sac Rest" final temperature has dropped to 141.8 degrees. Question: Did BTP calculate that 3.2 degree drop using the "Heat Transfer Coefficient" of the Mashtun or the Decoction Pot? Since that rest is happening in the Mashtun (the Decoction Pot is now empty, after all!), it should have been the Mashtun's "Heat Transfer Coefficient", right? But it wasn't. Here's the proof: Go to the Equipment list and edit your Decoction Pot's "Heat Transfer Coefficient" by arbitrarily setting it to 5.0. Then return to the schedule and notice that that final temp of the "Main Mash 1st Sac Rest" has changed to 138.7 degrees. Why should changing the Decoction Pot's value affect the temperature drop of a rest in the Mashtun vessel? On the other hand, if you then edit the Mashtun's "Heat Transfer Coefficient" to, say, 10.0, the "Main Mash 1st Sac Rest" final temp remains unchanged at 138.7, proving the Mashtun's heat value has no bearing on the rest's temperature drop.

I hope I have finally explained this clearly enough that Jeff and crew can understand what I mean, and either tell me where my assumptions are wrong, or say that it is a bug that can be addressed.

I explored this with the test recipe that I created to understand the decoction setup better. You are correct that changing the heat transfer coefficient changes the sachharification rest final temp. This is odd and must be a bug.

Perhaps Jeff or Lathe could explain the logic behind setting up a decoction if you and I are not getting it in the way that they intended.

Thanks for looking into this to confirm that I'm not crazy -- or at least, if I am crazy, then I'm not alone!

I don't think we want to document the work-around to a bug in the long-term wiki docs. But just in case it still isn't clear to anyone setting up a decoction, in order for the remainder of the mash to calculate correctly in the schedule, you have to set your Decoction Vessel to be your main mash tun. The only down side to doing that that I have seen is that the Heat To Boil Duration calculation will be wrong, but that is a lot less important than having the calculated temperature of some subsequent infusion being based on the actual starting temperature.